Conventionally, there is known an engine that emits an electromagnetic wave to a combustion chamber in synchronization with an ignition operation of igniting fuel air mixture in the combustion chamber. For example, Japanese Unexamined Patent Application Publication No. 2009-2219498 discloses an engine of this type.
More particularly, the engine disclosed in Japanese Unexamined Patent Application Publication No. 2009-221948, emits, during a compression stroke, the electromagnetic wave supplied from an electromagnetic wave emission device, from an antenna, while discharging at an electrode of a discharge device. As a result of this, plasma is formed in the vicinity of the electrode due to the discharge, and the plasma is supplied with energy from the electromagnetic wave. In the combustion chamber, a large amount of OH radical and the like is generated by the plasma, and combustion is promoted.